NASA's Robotic LRO Spacecraft Provides Data for Human Exploration

An instrument on LRO, Cosmic Ray Telescope for the Effects of Radiation (CRaTER), gauged the radiation dose of cosmic rays after passing through a plastic material that simulates how space radiation interacts with human muscle tissue. CRaTER initially was designed to characterize the global lunar radiation environment and biological impacts. Recent findings from data collected by LRO also may help scientists validate their understanding of the radiation environment and help engineers develop shielding that may reduce health risks to astronauts as they travel to an asteroid and eventually to Mars.

"We are actively sampling the radiation environment throughout the solar system so that we're prepared to send humans to a variety of destinations far from Earth," said Michael Wargo, NASA's chief scientist in the agency's Human Exploration and Operations Mission Directorate. "The data provided by LRO is an example of how the agency's robotic activities are informing how we develop our thinking on ways to execute future human missions."

The findings by space scientists from the University of New Hampshire and the Southwest Research Institute were published in the American Geophysical Union's journal, Space Weather. They provide in-space data without the influence of Earth's magnetic field, indicating lightweight, hydrogen-bearing shielding materials could enhance radiation protection for future spacecraft during space missions, confirming what ground studies and studies in low-Earth orbit have previously suggested.

Before CRaTER and recent measurements by the Radiation Assessment Detector on NASA's Mars rover Curiosity, the effects of shielding cosmic rays have been simulated in computer models, in particle accelerators and with observational data from NASA's Voyager and spacecraft in low-Earth orbit that are within the influence of Earth's magnetic field, like the now retired space shuttle and the International Space Station. Comparisons between plastics and aluminum were made in earlier ground-based tests using beams of heavy particles to simulate cosmic rays.

Two forms of radiation pose potential health risks to astronauts in deep space. One is galactic cosmic rays (GCR), particles generated by supernova explosions and other high-energy events outside the solar system. The other is solar energetic particles (SEP) associated with solar flares and coronal mass ejections from the sun.

Current spacecraft shield much more effectively against SEPs than GCRs. To protect against the comparatively low energy of typical SEPs, astronauts might need to move into areas of their spacecraft with extra shielding or employ other countermeasures. GCRs tend to be highly energetic, highly penetrating particles that are not stopped by the modest shielding provided by a typical spacecraft.

"Since its launch in 2009, LRO has been the source of numerous discoveries, generating tremendous excitement in the planetary science community," said John Keller, LRO project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "Data from the spacecraft is also providing useful evidence for those in the human space exploration community."